Servo-control valve for hydrostatic pumps



Sept. l,

1953 J. P. PoLoUEKToFF 2,650,542

SERVO CONTROL VALVE FOR HYDROSTATIC PUMPS Filed NOV. 19, 1948 161 /A j 160 o 154 134 13 ix 16g O O S:`:: 5,5/ O

12 12a 139 ua L- 12724 aald ys' /9 138 12 zo 0 /37 53 zo gr Z6 /49 a? l n s Q a l 1f-f J 4 P /29- so M3 130%/ /3/// las :I 145/ 142 H r /N VENTO@ Patented Sept. l, 1953 SRVO-CONTROL VALVE FOR HYDROSTATIC PUMPS Jean Paul Polouektoff, Paris, France 'Application November 19, 1948, Serial' No. 60,905 'In France November 20, 1947 9` claims. (ci. loa-5) The present invention relates -to -a hydraulic servo-control valve that provides automatic and uninterrupted operation `of immersed pumps in which the filling-is produced by the hydrostatic pressure with or without the assistance of an injector, whereas the delivery is produced by the pressure of a fluid, for example compressed air, on the liquid to be delivered.

A plant of thistype-essentially comprises a pump formed of two containers associated with an air distributor which successively and alternately places one of the ends of each of the containers in communication with'the compressed air supply and* with the -air exhaust pipe, `while the opposite ends of said `containers are alternately and `successively placed in communication with the delivery pipe for the liquid and with the inlet ports for said liquid, so that each ofthe containers is inthe delivery phase while :the other is in the lilling phase and vice-versa.

The change ofphases in existing pumps of this type is produced by the movement of a groupof iloats which actuates the air distributor.

The floats have theffollowing drawbacks:

l. The emptying of the compartment in` which the pump is immersedis limited by the minimum height required for the operation of the floats.

2. In orderV to be su'fciently reliable in operation, the iioats mustvbe fairly buoyant` and .be fairly heavy, thereby involving a correspondingly large size and limiting the minimum dimensions of the cylinders.

3. There is danger of the oats being burst by the pressure of the air-when the particular conditions of use of the pump require a' high pressure.

I-leretofore this has prevented the manufacture of` pumps of this type of small size and 10W output for which there is a demand in certain branches of industry, for example in boring operations.

The present inventioniovercomes these `various drawbacks and provides a servo-control valve which automatically controls the distributor of pumps of thetype in question, without involving the use of anyffloat.

The chief advantages and features fof this servo-control valve will become `apparent from the ensuing description' made fwith reference to` the accompanying drawing, the single'iigure .of which shows a longitudinal Section Aof an` embodiment of a hydrostatic pump provided with-a servo-control valve accordingto the invention.

The hydrostatic pump to which the servo-control valve according tothe inventionl1as` been assumed to be applied,r essentially comprises a 4container 3-and a container Arwhichnmay. beaof 2 any shape (cylindricalor otherwiseiand may be superposed, separate or contiguous (it is the latter case that has been illustrated). These two containera` which are f substantially thel same volunie and are adapted to operate successively, form the twocy-linders of thepump.

These two cylinders v3 and 4 are bounded at their upper part by a delivery chamber 5 and at their lower` part' by a suctionchamber' which is connected to the cylinders through inlet valves 8a, 9a, whereas the chamber 5 is connected to said cylinders through delivery valves Sr, Sr. Said valves Sr, 91",.may1beconstructed in any suitable known manner, but they are `loaded in such a manner as to produceaconstant pressure-drop of a predeterminedminimum value (for example 0.150 kg. per sq. cm.).

Said two cylinders. xand'll are `alternately and successively placedin communication, by means of. a distributor, either with a source of compressed air i2 v(or. ofsteam), orwith the exhaust pipe t3. According to amodification, said exhaust pipe` could lbe connected to thesuction pipe of the compressor.

The distributor comprises a body |91 in which a balanced piston-valvol is .adapted to move. Said body I9V is `adapted'to be placed incommunication:

c. With the source ,of `compressed-airIZ by means of the ducts! l` which opens into said body throughthe port. 22, a pressure regulating device, which will 4be described hereinafter being inserted between said lductlZl and' the source |21.

b. Through the ports. 23 and 23a and the duct 261, either, as shown, with the surrounding medium (water or atmospheric air) which surrounds the upper cover `of lthe :delivery chamber 5. or, according to the:` modification hereinbefore consideredwith the suction pipe of the compressor.

c. With the ,upper part of. the cylinder 3 through a port25and aduct26.

d. With the upper part' of the cylinder 4 through a porttZlianda pipe 28.

The distribution valve? 20 may assume two positions:

a. The highi position (position shown) in which it places in communication, on the one hand, the cylinder -4 .withthemompressed air supply pipe l2, and, on the other hand,xthe cylinder 3 `with the exhaust pipe I3.

b. The low position,v in which it places in cornmunication, onV theone hand the cylinder 4 with the exhaust pipe I3, and on the other hand the cylinder 3- with the compressed air supply l2.

vAccording to the present invention, said piston- `valve 2c is abruptly shifted from one position to the other, and conversely, by the action of a servo-control valve comprising a balanced pistonvalve |24 adapted to move in a cylinder |25 by the reciprocating action of a push-rod i?^` secured to a piston |21 adapted to move in a cylinder i28 and of a push-rod |29 secured to a piston |33 adapted to move in a cylinder l3i.

Furthermore, the piston-valve |24 is subjected to the action of a lever |32 on which a spring |33 acts by means of any suitable device, for example a ball. Said spring |33 may be of any suitable type (helical, spiral or other type) and its adjustable tension is determined as will be described hereinafter.

IThe outer end of the cylinder |28 is connected through a pipe |34 to the cylinder 3 and the outer end of the cylinder |3| is connected through a pipe |35 to the cylinder 4.

The inner ends of the two cylinders |23 and I3! are connected through the pipes |35 and E31 to the delivery chamber 5. This connection may be effected in two ways:

a. Either directly, in which case the pipes |35 and |31 are iilled with the liquid delivered which passes beforehand through a iilter i3d.

b. Or indirectly, in which case the pipes i3d andV |31 are filled with oil or any incompressn ible liquid, the pressure in the chamber 5 being transmitted to said liquid by a suitable fluid-tight diaphragm which replaces the filter.

1n both cases, the flow of the liquid through the pipes |36 and |31 can be braked at will by means of the twoadjusting screws |39 and ist.

The cylinder is provided with a plurality of ports, viz., a central port |5| connected through a pipe |52 to the source of compressed air i2 on the upstream side of the pressure regulator which will be described hereinafter: a port |53 connected through a pipe |511 to the upper part of the cylinder I9 of the distributor; a port |55 connected through a pipe |55 to the lower part. of this same cylinder; and two ports i515 and |58, one at the upper part, the other at the lower part of the cylinder |25 and both connected to the exhaust pipe 24.

The valve |24 can assume two positions:

a. A high position, in which it places in coinmunication, on the one hand the top of the cylinder |9 Vof the distributor with the source of compressed air i2 through the ports |5| and |53 and the pipe |54, and on the other hand, the bottom of the cylinder |9 with the exhaust pipe 24 through the pipe |56 and the ports E55 and |55.

l). A low position, in which it places in cornmunication, on the one hand the bottom of the cylinder l@ with the source of compressed air` l2 through the ports |52 and |55 and the pipe and, on the other hand, the top of the cylinder i9 with the exhaust pipe 24 through the pipe ld and the ports |53 and |51.

In the position shown in the gure, the distributorV has just been shifted into the high position and the pressure fluid is beginning to be admitted through the port 21 and the pipe 23 into the pump cylinder 4 which is then in the delivery phase. The manometric pressure in said cylinder is then equal to:

wherein Gx is the hydrostatic pressure in the delivery -chamber 5 and Ap the internal pressuredrop in the pump, in particular in the internal pipes and the delivery valves 81, 9T. Said pressure P acts through the pipe on the Ylower 4 face of the piston |35 of the servo-control valve.

On the other hand, in the cylinder 3, which starts in the lling phase, there is only the hy drostatic filling pressure H which acts through the pipe i313 on the upper face of the piston |21. Thus, in the position shown in the figure, the piston |33 is subjected on its lower face to the pressure P through the pipe |35, and on its upper face to the pressure Ga: through the pipe |31; during the saine period, the piston |21 is subjected on its lower face to the pressure Gx through the pipe |36 and on its upper face to the pressure H through the pipe |34.

The piston |35 is therefore urged upwards by the diierential pressure Ap. The piston 21 is likewise urged upwards by the diierence between the two pressures G-H.

Since the piston |21 is independent of the piston-valve |25 and of the piston |33, its movement by the actionV of (Gm-H) can take place separately and does not exert any effect on the movement oi the piston |33 and of the pistonvalve |2i, which remain solely affected by the differential pressure Ap and the spring |33. rlhe differential pressure Ap thus causes the pistonvalve |23 to move upwards. At the beginning of this movement, said piston-valve closes the port 555, but the compressed air conned in the pipe |55 continues to retain the balanced piston-valve 25 oi the distributor in the high position. During the first half of its stroke, the piston-valve 82d tensions the spring |33 which then assists in the completion of the second half of said stroke at the end of which said piston-valve |24 places the port |53 in communication with the compressed air inlet port |5| and the port |55 in communication with the exhaust pipe |58. The compressed air thus acts on the upper face of the piston-valve 23 of the distributor and abruptly moves it into the low position, thereby reversing the phases or the operation of the two pump cylinders. The cycle of operations thus continues without interruption.

The pressure in the cylinders 5 and 4 can be 'transmitted to the pistons |21 and |30, either directly by means of the liquid delivered, or by means of a liquid that fills the pipes |34 and |35 which are duid-tightly closed and are provided with diaphragms at the lower part thereof.

rilhe action of the spring |33 constrains the piston-valve l23 to travel up to one of its extreme positions, thereby ensuring the starting of the pump after it has been stopped. The movement of the piston-valve |24 cannot be abrupt owing to the hydraulic braking exerted by the liquid that iills the pipes |33 and E31 and the section or" 'which is reduced by the adjusting screws |35 and rThe more or less complete closing of the passage enables the movement of the pistons |21 and ltd to be more or less slowed down and, consequently, Vother things being equal, the movement of the piston-valve |25 to be slowed down and the changes of phase of the pump to be spaced a longer time apart and therefore the speed of the pump to be reduced.

It is obviously necessary for the differential pressure Ap (which corresponds to the pressuredrop) to be sufcient to cause the piston-valve i243 to move, and for said pressure to be constant in order to ensure a smooth operation of the pump.

This result is obtained, on the one hand by loading the delivery valves 8T and Sr, and on the other hand by means of Athe pressure regulator hereinbefore mentioned. It has, in fact, been shown 4that the iirerentiai pressure Ap=P-Gr. Now, G varies with` theheight of delivery. 'The pressure P must therefore .vary under the same conditions. This is what enables the pressure regulator to` be obtained.

This regulator, which is inserted between `the air supply pipe |,2 and the ductv 2| of the air distributor, essentially comprises a balanced valve 4] adapted to move in a cylinder 48 which is provided with an opening '49' through which are compressed air enters said cylinder, and with two openings 50 Vthrough which said air reaches the duct 2l and thence flows into the distributor. Said valve 41 is controlled by a hydrostat 5| formed by a deformable member 52 (piston, diaphragm, bellows or` any. other like member) which is subjected; on the one 'hand to the hydrostatic delivery pressure Gx, and to the action of the counterweight 53, and on the other hand to the pressure P of the air in the cylinder 48. At the initial adjustment, the counterweight is adjusted in such a manner that for a predetermined hydrostatic pressure G, the valve 41 is in a position in which it uncovers the opening 45 to such an extent that the pressure of the compressed air is the pressure required to effect the emptying of a cylinder in the desired time T2, equal to the filling time T1. If the pressure of the air falls below the useful delivery pressure, the valve 41 moves downwards and opens the port 40 Wider, thereby increasing the pressure to the desired value. Conversely, if the pressure of the air becomes greater than the useful pressure, the valve 41 covers the port 49 more. An automatic regulation of the pressure P of the air is thus obtained. The time T2 required for the delivery will therefore be kept practically constant, irrespective of the value of Ga: and for each of the cylinders 3 and 4, and can be adjusted by acting on the screws |39 and |40.

In order to prevent water from entering the ducts of the distributor, a floating valve |50 is provided at the end of each of the pipes and 28 that connect said distributor to the cylinders 3 and 4, so that when the water reaches the upper part of the corresponding cylinder, said valve |50 is lifted and hermetically closes the end of the associated pipe.

The lling of the pump cylinder 3 is assisted by an injector |42, by means of the pressure set up in the adjacent cylinder 4 which is in the delivery phase. An identical injector |43 performs the same function for the cylinder 4. These injectors |42 and |43 operate with water or with compressed air. They enable the pump to effect the complete draining of the compartment in which it is immersed and even of imparting to said compartment a certain suction power.

In the compressed air supply pipe |2 is inserted a butterfly-valve |60 which is retained by a float |5| in the open position so long as the level of the water to be pumped is above the upper part of the pump. When this level falls below this limit, the butterfly-valve |00 assumes the closed position in which the compressed air can only pass through the perforations |62 provided in said butterfly-valve.

It is moreover obvious that the invention has only been described and illustrated herein in an explanatory and in no way limitative manner and that any useful modifications may be made therein without exceeding its scope.

I claim:

1. A hydrostatic pump combination comprising a housing having two alternately acting pump 6 cylinders, a delivery chamber and a suction chamber, connections between said pump cylinders respectively and said delivery and suction chambers, delivery and inlet -valves controlling said connections, an exhaust pipe, a source of compressed fluid, a distributor alternately and successively placing in communication said pump cylinders with the source of compressed fluid and with the exhaust pipe, a servo-control valve in fluid communication with the distributor abruptly actuating said distributor and comprising a balanced piston-valve, two oppositely located cylinders, a piston working in each of said cylinders, means operatively connecting each of said pistons to said balanced piston-valve, one of said two cylinders being connected, to one of the two said pump cylinders, and the other of said cylinders being connected to the other of said pumping cylinders, and said cylinders being connected to the said delivery chamber of the pump, whereby the pressure P=G+Ap (wherein P is the pressure of the compressed fluid, Gm the.`

hydrostatic delivery pressure, and Ap the pressure-drop) in the pump cylinder which is in thev delivery phase actuates the piston in the cylinderr connected to said pump cylinder by engaging one.

face thereof, the opposite face of the piston being, subjected solely to the action of the delivery pressure G P, whereas the piston in the opposite cylinder moves independently in the same direction due to the fact that it is subjected to the differential pressure between the delivery pressure Gx and the hydrostatic filling pressure H G.

2. A hydrostatic pump combination according to claim 1, wherein the distributor has opposing ends adapted to be placed in communication selectively with the source of compressed fluid and with the exhaust and the balanced piston-valve thereof is successively moved by said pistons from a first position, in which position it places the compressed fluid supply in communication with one end of the said distributor of the pump, and the other end of said distributor in communication with the exhaust, thereby causing the .said distributor to move into one of its two possible positions and to be retained in that portion, into a second position in which the connections are reversed, whereby at the end of each stroke the servo-control valve controls the distributor to place one cylinder of the pump in the filling phase and the other cylinderv in the emptying phase, or conversely.

3. A hydrostatic pump combination according to claim l wherein a spring is provided and is positioned to be tensioned by the piston-valve during the irst half of its stroke from the rst` portion to the second position, said spring biasing said piston-valve during the completion of the second half of the stroke.

4. A hydrostatic pump combination according; to claim l wherein in order to make the differential pressure `Ap=PGar sufficient to actuate the piston-valve thereof, means are provided to increase said pressure by loading the delivery valvesv of the pump.

5. A hydrostatic pump combination according to claiznl wherein in order to make said differential pressure remain substantially constant irrespective of the variations of the hydrostatic delivery pressure, means are provided for automatically regulating the pressure of the compressed fluid proportionally to said hydrostatic pressure Gx.

6. A hydrostatic pump combination according to claim l wherein means are provided for automatically regulating the pressure of the compressed iuid, said means comprising a regulator connected to the distributor, a Valve controlling the connection between the regulator and the distributor, an adjustable counterweight acting on said valve in couple with the action of the hydrostatic pressure Gx and said Valve being subjected to the pressure of the compressed uid admitted to the distributor, said regulator controlling said valve which opens more or less the inlet of said compressed uid.

'7. A hydrostatic pump combination according to claim l wherein means are provided for regulating the duration of each of the. two strokes of said piston-valve.

8. A hydrostatic pump combination according to claim 1 wherein a connection is provided between the said cylinders and an adjustable hydraulic brake is operatively attached to said cone nection between the cylinders to control the fluid ow therethrough and brake more or less the movement of each'of the two pistons that actuate the piston-valve, in order to control the duration of each of the two strokes of said piston-valve.

9. A hydrostatic pump combination according to claim 1 wherein an injector is provided for each of the two pump cylinders and is supplied with the pressure uid fed to the pump cylinders when they are in the delivery phase, in order to assist in the lling of either of the pump cylinders, in particular when the level of the water to be pumped is near the bottom of the pump.

JEAN PAUL POLOUEKTOFF.

No references cited. 

